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October 26, 2010

East Asian jaw from 100,000 years ago is 'modern human'

The Zhirendong jaw from Guangxi Zhuang (South China) was discovered in 2007 (but I did not know until late 2009). Its most striking characteristic is the chin, which is a trait typical of Homo sapiens. Now a paper co-authored by palaeontology superstar Erik Trinkaus says we are before a modern human jaw, maybe admixed with other Homo species.

The 2007 discovery of fragmentary human remains (two molars and an anterior mandible) at Zhirendong (Zhiren Cave) in South China provides insight in the processes involved in the establishment of modern humans in eastern Eurasia. The human remains are securely dated by U-series on overlying flowstones and a rich associated faunal sample to the initial Late Pleistocene, >100 kya. As such, they are the oldest modern human fossils in East Asia and predate by >60,000 y the oldest previously known modern human remains in the region. The Zhiren 3 mandible in particular presents derived modern human anterior symphyseal morphology, with a projecting tuber symphyseos, distinct mental fossae, modest lateral tubercles, and a vertical symphysis; it is separate from any known late archaic human mandible. However, it also exhibits a lingual symphyseal morphology and corpus robustness that place it close to later Pleistocene archaic humans. The age and morphology of the Zhiren Cave human remains support a modern human emergence scenario for East Asia involving dispersal with assimilation or populational continuity with gene flow. It also places the Late Pleistocene Asian emergence of modern humans in a pre-Upper Paleolithic context and raises issues concerning the long-term Late Pleistocene coexistence of late archaic and early modern humans across Eurasia.

Not quite sure what discussion you mean right now or how it relates to this, sorry.

"Laconic" I must be, as we are dealing here with a piece of evidence, however one that stands almost alone and is controversial. The sources emphasize the supposed "admixture", which I do not see too clear, so the best I can do is to mention the matter as it stands now and let it be there as reference for future discussions.

What was that other remain that sparked some talk last year? It was from China, from about 100,000 years ago, and it was a lot more complete, several pieces of the cranium, including forehead. The Chinese claimed it was a modern human, but non-Chinese paleontologists thought it was more like "almost" homo sapiens. If there was doubt about that one, with almost half the skull available, how sure can one be of this one, with a part-jaw and 2 molars? Though having a chin I guess is a huge point in its favor.

"Not quite sure what discussion you mean right now or how it relates to this, sorry".

Sorry i should have been more specific. My bad. I refer to the one about a possible northern OOA dispersal i/o southern coastal route several weeks ago. I think Dienekes is doing a good analysis of the situation if finaly this result (AMS 100 kybp in EA) finding is confirmed. Of course this result, if true, does not confirm in any way the northern route, but makes it more likely.

@Carpetanuiq: Well, Dienekes doesn't say much more than I do here. It is indeed strongly suggestive of a H. sapiens colonization in the >100 Ka time-frame. This was the case a year ago also, just that back then Trinkaus had not blessed yet the conclusion in a peer reviewed paper.

The jaw is from SE Asia, it says nothing about any conjectural northern route, specially not when there are also possible H. sapiens tools (with blades: mode 4) in South Asia by about the same dates (and nothing of the kind in the North).

@Argiedude: looks like a H. erectus, right?:

"The fossil consists of 16 pieces of the skull with protruding eyebrows and a small forehead".

It could indicate a northern refugium for H. erectus as H. sapiens advanced. Hard to say.

It's a different skull in any case and points in the opposite direction, it seems to me.

"it says nothing about any conjectural northern route, specially not when there are also possible H. sapiens tools (with blades: mode 4) in South Asia by about the same dates (and nothing of the kind in the North)".

But surely we've been consistently cautioned not to associate specific tools with the presence of H. sapiens.

"The 2007 discovery of fragmentary human remains (two molars and an anterior mandible) at Zhirendong (Zhiren Cave) in South China provides insight in the processes involved in the establishment of modern humans in eastern Eurasia".

What the discovery tends to indicate is that our origin is not simply a product of the migration of a small population out of Africa, who replaced everyone else. It is the result of a much more complicated process.

Read my lips: political South China is part of geographical and ethnographic South East Asia. How many times I have to go through that?

"But surely we've been consistently cautioned not to associate specific tools with the presence of H. sapiens".

Say what?

Harrods thinks otherwise, Hoffecker thinks otherwise and I also tend to think otherwise. Toolkits is often the only evidence we have so we must interpret them within the broader context, even if there's some risk. If we are to wait till enough skulls show up, we will become skulls ourselves.

"What the discovery tends to indicate is that our origin is not simply a product of the migration of a small population out of Africa, who replaced everyone else. It is the result of a much more complicated process".

That's not what I think. Regardless of rare frontier admixture events, the process seems one of replacement, otherwise we'd see a lot more Neanderthal blood in us. It's even possible that admixture with non-Ergasters was just out of the biological possibilities.

I have already discussed that, even when admixture is biologically possible, people tend to marry and reproduce within their own community and may even act up racist towards other species, specially if these are furry.

There's anyhow a degree of potential confusion between "archaic" Sapiens and "archaic" human (in general) traits. If the jaw looks mostly H. sapiens, we are probably before a H. sapiens and not any hybrid.

The site is actually pretty close to the coast (~100km), and very close to Vietnam.

Yet, it still could have been populated via NW India and northern Myanmar instead - especially, if at the time erectus was prevalent in the rain forest regions.

Given that heidelbergensis (or related) made it all the way to China, there really shouldn't be a surprise the earliest AMHs were able to do the same - although perhaps something changed ~60,000 years ago that made AMHs - at least the ones outside Africa - so much more successful. Perhaps we needed a second wave of input from Africa - the first wave may have just been too small, too idiosyncratic, and perhaps too diluted with Neanderthals/heidelbergensis.

In the end, only DNA analysis will tell us to what extent ancient populations actually survived and had an impact. Populations as this one may have had none or only a very, very limited impact on extant populations.

"Perhaps we needed a second wave of input from Africa - the first wave may have just been too small, too idiosyncratic, and perhaps too diluted with Neanderthals/heidelbergensis".

Could be. Still I just posted on some study on mice colonization and the prospect seems to be that the first colonization would fend off well against secondary waves, everything else equal. Things were not equal surely between H. sapiens and H. erectus but I see no apparent reason (other than climatic fluctuations in some places) to allow for major recolonizations before Neolithic. Of course, Paleolithic tech and economy can have many variants, some possibly with an advantage of sorts, but knowledge is also easily transmitted between groups, very specially practical knowledge (know-how) - so advantages of this kind are likely to be easily offset unless they are largely biological.

I find difficult hence to accept the existence of two waves, specially when there's no particular evidence in favor of any such double wave model. You're probably thinking in terms of molecular clock estimates but they are likely to be wrong, short from the real thing.

Guangxi is now full of Zhuang peoples of Tai origin which itself are of north origin. So as Eurologist says, this purported chined chinese AMS could have been arrived there from West India, but perfectly also from North trough Yangtze valley. We just don´t know.

2. What we do know for sure, if we use the experiments of the past that pre-history brought us, is that there has been in the past at least 3 OOA from the genus Homo, and possibly 4, all in interglacial times (http://en.wikipedia.org/wiki/File:Atmospheric_CO2_with_glaciers_cycles.gif):

--first, 2 Myrbp where the H. Antecessor occupied Europe and China, --second, 600 kyrbp, interg. Aftonian I, H. Heidelbergensis and H. Neanderthal in Europe and ¿also in EA? IDNK. maybe someone can clarify. --possible third, interg. RW around 120-100 kyrbp. where we find H. sapiens in Levant and possibly in China.--alternative third or fourth, current paradigm around 60 kyrbp.

Why in the two first interglacial cited above there were OOA and northern route but in the third RW there was not succesfull H.sapiens OOA, and if it was there was not northern route ? That´s what should be explained.

"Why in the two first interglacial cited above there were OOA and northern route but in the third RW there was not succesfull H.sapiens OOA, and if it was there was not northern route ? That´s what should be explained".

I am not aware of any "northern route" in the other migrations either. Eventually some (highly derived) Neanderthals and "erectus" would reach high latitudes but they needed a lot of time.

"Of course, Paleolithic tech and economy can have many variants, some possibly with an advantage of sorts, but knowledge is also easily transmitted between groups, very specially practical knowledge"

Earlier you wrote:

"people tend to marry and reproduce within their own community and may even act up racist towards other species"

Wouldn't that situation limit the transfer of technical knowledge?

"I find difficult hence to accept the existence of two waves, specially when there's no particular evidence in favor of any such double wave model. You're probably thinking in terms of molecular clock estimates but they are likely to be wrong, short from the real thing".

If we care to take the estimates at face value we do see that mtDNA is older than Y-haps.

If my data are wrong, then my source is wrong and it could be: it is a 2006 source and from a highly reliable and well informed science writer but not specialist. Good or wrong, I think it could be a good approach to check what happened in previous runs of the OOA event so i´m more interested interested in knowing the uncontroversial most updated data about this matter (not the interpretations) than to defend my data in previous comment. Unfortunatelly it seems that also regarding the homo genus number of species, phylogenetic relations and previous expansions we are walking on the moving sands of controversy: for instance http: http://en.wikipedia.org/wiki/Homo and http://en.wikipedia.org/wiki/Homo_erectus.

First OOA, we agree the dates, we agree origin. My source describes some Homo found in Dmnisi, Georgia (Homo georgicus) and later about some tools in China (Majunguo) similar to those used by these georgian homos. Since these tools are not associated with fossils i agree it is controversial to match it with these georgian homo, even if this was the first homo OOA. In any case at this time it could be ergaster or erectus. Here we have two possibilities. Either they two diferent species, either they are the same. In any case fossils of both-same spacies are found in north eurasia asia or east asia and south east asia, but not in arabia nor south asia (India). Correct ?

My second OOA. My source says that those homo involved in this second OOA (dated around around 600 kyrbp were the ancestors of H.Neanderthal and H.heidelbergensis and that these caused the extinction of H. Antecessor a remain species of the first (my first) OOA. This is in contradiction with your second OOA which is sooner and makes some speciation and phylogenetic relations assumptions. Are these assumptions uncontroversial ? I think it is still unclear that ergaster and erectus were not same species...What are the evidences that erectus and ergaster were diferent species ? What are the evidences of Ergaster>>Antecessor>>Heidelb.>>Neand. ? Genetic, lithic, fossil or both fossil-ltithic in same paleosites ? Sources pls.

Again we are facing several possibilities ((a second OOA at 1 Myra and no third OOA at 600 kyrbp) or (a second OOA at 1M and a third OOA at 600 kyrbp) or (only a second OOA at 600 kyrbp). In any case, these again went to the north (Europe). Am i correct ? And from there it seems more likely to reach EA trough a northern route than trough a southern (i agree that my last sentence is just speculation). I find weird a not OOA at 600 or at least expansion to Central Asia or even EA from Europe. They missed an interglacial, a time surelly full of opportunities for expansion...

About the third OOA, again we agree on dates and it coincides with an interglacial. My source says this was by made by Homo sapiens, that it expanded all over Eurasia with no more details (only that these caused the extiction of all other Homo species) so it is not really informative. Before Zhirendong the consensus was that this one was unsuccesfull and stoped at Levant.

Then there are some consensus about a fourth fifth) OOA at 60 kyrbp trough a southern route, based mainly on genetic data.

Minor flows or contacts can perfectly transmit loads of technical practical information without adding almost any genes. If the Hadza adopt a Bantu, this one can teach them a lot of Bantu stuff (some of which may be useful or simply becomes fashionable and is incorporated). But the gene flow is minimal or even zero maybe.

"If we care to take the estimates at face value we do see that mtDNA is older than Y-haps".

I fail to see that. I agree that mtDNA diversity seems to survive better but I still see strong parallels between mtDNA and Y-DNA lineages beginning with mtDNA L0 and Y-DNA A.

"What are the evidences that erectus and ergaster were diferent species ?"

AFAIK little, mostly the were living in different places with different techs maybe after almost 1 million year of divergence. I don't mind if you call both "erectus", really.

"What are the evidences of Ergaster>>Antecessor>>Heidelb.>>Neand. ?"

For that read Arsuaga or the others of the Atapuerca team. It's mostly working with skulls (few), bones, teeth and possibly tools too. For what I've read it's very consistent but I am no expert anyhow.

"In any case, these again went to the north (Europe). Am i correct ?"

I don't have clear evidence that the "Levallois migration" some 600 Ka ago ever happened, I can't really track it. For what I know Levallois appears scattered in very diverse areas.

Yes, if you wish to include the ghostly "Levallois migration". The Acheulean migration is well documented (ref 1, ref 2): it affected West and South Eurasia anyhow. This may explain the "modern archaic" of Patpara.

"And from there it seems more likely to reach EA trough a northern route than trough a southern (i agree that my last sentence is just speculation)".

Seems logical to me. And for much of prehistory there has been a well-defined line between India and Se Asia, the Movius Line.

"Right? Thanks".

Correct. But this paper deals with just a small region of Siberia. I still can't find the one I linked to on your blog regarding the continuity in lithic technology across Central Asia from the Altai to the Amur over the last 160,000 years.

"What are the evidences that erectus and ergaster were diferent species ?"

As Maju alluded to, it is partially a matter of convenience to make that distinction, but also reflects the reality that these populations evolved on separate continents for 1 to 1.5 million years. There is a fairly good record of continued and interrelated development in Africa and adjacent Europe and west Asia, while erectus does not appear to participate in any of this - from the morphology to the tool sets.

"What are the evidences of Ergaster>>Antecessor>>Heidelb.>>Neand. ?"

Again, that seems to be well-documented and is widely agreed upon. Some don't make a distinction between antecessor and heidelbergensis: they are only separated by 200,000 years or so.

Neanderthalers seem to be a special cold adaptation, originally limited to Europe, with much later spread East (covering Turkey, Iran, Afghanistan, Kazakhstan, and perhaps all the way to the Altai range - east of Turkey/Iran perhaps only as late as 60,000 years ago). I have to check the Altai claims as to whether they would rather fit more closely heidelbergensis, as IMO the Chinese sites do.

There is really no evidence that Neanderthalers progressed cognitively or in their tool set from heidelbergensis - if anything, they seem to be more highly specialized: in body type, very short hunting range, and low food diversity.

I tend to think that the far eastern sites are more directly derived from heidelbergensis rather than Neanderthal. They date from between 100,000 to 200,000 years ago, and seem to reflect an earlier movement East than the sites from Iran to ~Kazakhstan.

I haven't looked at the data in a long time, but from what I recall the skeletons and cranium size all favor heidelbergensis over Neanderthal. And the (slightly) more modern tool set (and likely the full control of fire) just arrived with these - so there is nothing that points to some parallel development in east Asia. In comparison, the contemporaneous erectus in the far East seems to have stagnated and far less advanced.

--Regarding the paleovegetation and climate there is a great web page. http://www.esd.ornl.gov/projects/qen/

--Regarding an updated systematics (number of accepted homo species, their phylogenetic relations and speciation process) of the genus homo I´ve been looking for some phylogenetic tree but all of them seems quite old or inaccurate. For instance

It seems that there is not a definite systematics of this genus yet, although what you say about ergaster-erectus seems reasonable.

In any case IMO from erectus-like (non intelligent tools user) to sapiens-like (intelligent homo) you do not need any sort of miracle not even any kind of cladogenesis, just a very likely single mutation of some of the 22 skull bones. Once you´ve got lithism (hability of use tools, present in erectus-like) you do not need big mandibles. This lives a lot of room for evolution experimentation with mandibles-skull muted individuals which would have starved without the use of tools and therefore skull variability within a same species. So the transition erectus-lithic to sapiens could have happened in any place assuming enough time, big sized demographics and high skull variability is expected. But I wonder what´s the role of the chin (which seems to be related with modernity) in all this ...

The chin seems to be related to efficiency in chewing: it reinforces the bone so greater strengths can be applied by the muscles without breaking it. This is an important detail in such a light-boned species as ours. I've read somewhere (can't find it now) that, thanks to the chin, our bite is more powerful than that of Neanderthals, even if their jaws and teeth and general musculature was all larger and more robust than ours.

Another possibility would be that the chin is related to speech (point of support of facial, specially lips' movements).

Additionally there may be some sexual selection involved if men with somewhat prominent chin (along with other traits) are considered more masculine and hence generally more desirable. On the other side women with too strong chin may look less feminine... so maybe this is canceled unless gender-imprinted.

Finally the chin serves to point: it's an extra pointing finger and among Basques at least the usual uncompromising street greeting is raising the chin slightly and saying, sometimes, if you feel expressive, "ep!" It takes less effort than pointing with both fingers and making a posse a rapper-style, and helps when you are carrying stuff or children around as well.

I think that the chin is the best communicational invention after the blank of the eyes, which also serves to point (with the iris) quietly and economically. But the key value may be in chewing help.

As for the graphs, not one seems to include the distinct category H. rhodesiensis, what makes matters more complicated. See these maps. Rhodesiensis is the African equivalent of Heidelbergensis (leading to Sapiens instead than to Neanderthals) but they are not connected geographically in any way.

1. Your´s an interesting comment on the chin. Multifunctional now, then. The original function was possibly the one you point to. I was thinking about its relation with language

2. I´ve found yet another phylogenetic tree, the Arsuaga-Martinez proposal (no dates about when the proposal was done! no dates about the updates !).

http://www.nuestrosorigenes.com/

This one includes the Rudolfensis. What about East Asia ? Did an intermediate homo evolved there independently or was it imported ?

3.I see clearly the transition chimp>australopithecus-like (bipedism)and the transition australopithecus>erectus (lithism). But the transition erectus>advanced homo (I may include here Heidelb., Neands.,Rudolf.,Sapiens or at least Neands. and Sapiens)seems to me quite fuzzy. It seems more a matter of degree and optimization than a discrete step. Bigger skull surelly means automatically bigger brain and bigger brain means better and more efficient thinking (computationally speaking, we know that with more space we can do more things and quicker), but there must be an optimum (besides this optimum you need more energy and more time for communication processes). Of all these evolutionary experiments allowed by the lift up of the big mandibule constraint in Erectus (Neands...), Sapiens was surelly the optimum. Just speculation, of course.

I wonder how many genes control the skull shape and size and how these are related with the genes of brain size. The easist would be an instruction like "grow as much as to fill the skull"...

The main reason is that I learned withing the old school in which all between H. habilis and "modern" species (H. sapiens and H. neanderthalensis) is "H. erectus". H. ergaster, H. heidelbergensis, H. rhodesiensis are just variants of H. erectus. Hence H. erectus cannot descend from H. ergaster, which is the evolved African variant of H. erectus. It is the other way around.

That they haven't been able to come up with better names for Asian H. erectus variants is not a reason to place H. erectus downstream of H. ergaster. Also H. ergaster is not really defined by any biological characteristic but by using Acheulean technology anyhow, so again its predecessors with Olduwayan/chopper industry must be something else: H. erectus.

The other reason is that I know of no reason to make any particular connection between H. antecessor and H. rhodesiensis/sapiens. IMO H. antecessor is antecessor only to H. heidelbergensis/neanderthalensis.

The fossil maps linked above show that while the European and African branches, leading to Neanderthal and H. sapiens were clearly evolving, there was all the time a Mediterranean belt of H. erectus (read H. ergaster, as neither my source nor me bothered with the subtle distinction).

This strongly suggests that there was no meaningful connection between the two most dynamic branches of Paleolithic Humankind but that evolved separately (in parallel).

"Did an intermediate homo evolved there independently or was it imported [in East Asia]?"

IDK. H. erectus and H. ergaster evolved in Africa. H. heidelbergensis in Europe. But we know little about the exact taxonomy of Asian specimens, which are generally dumped into the H. erectus category. Someone commented before that he thinks late Asian Homo are H. heidelbergensis. If that's the case, then Europe should be the origin, as far as we can tell.

The most intriguing anyhow is the Patpara skull (c. 200 Ka ago) which is the largest of its epoch by far, actually in the Neanderthal/Sapiens range or almost. But it's an isolate fossil and without more materials nothing can be said for sure. It's from South Asia anyhow.

"I see clearly the transition chimp>australopithecus-like (bipedism)and the transition australopithecus>erectus (lithism). But the transition erectus>advanced homo (I may include here Heidelb., Neands.,Rudolf.,Sapiens or at least Neands. and Sapiens)seems to me quite fuzzy".

Specially it is a growth of brain capacity. Earliest Homo (H. habilis), with just 600 cc, were more in the chimpanzee range (350 cc) than ours (1400 cc). If you see a cranial capacity graph, you soon notice that, in spite of the blanks and individualized variation, there's a clear tendency to increase the brain capacity. The first such step is taken by H. erectus c. 2 million years ago, reaching maybe 800 cc on average, then "evolved erectus" (ergaster, rhodesiensis) reach to 900 or 1000 cc. Patpara is in the 1200 range and we are even higher, as were Neanderthals.

So there is not a clear radical change but doubling or more the brain size (and presumably quality too). Some have argued that there is something called "modern human behavior" defined by symbolism but the fact that Neanderthals also show such capacity for symbolic (artistic, ritual) expression emphasizes that the two big-headed species were not so different even if they evolved separately for a million year or so.

However it is also true that the oldest symbolic behavior registered belongs to H. sapiens (Palestine 120,000 years ago, North Africa soon after and South Africa c. 60 or 70 Ka ago).

"It seems more a matter of degree and optimization than a discrete step".

Well, sure. But chew on this: while Neanderthals may be overall 10% different from us (in relation to chimpanzee/bonobo) they are only 2% (exactly 1.7%) different from us in the HARs, regions of rapid evolution in the human lineage. This indicates that they were five times more "human" in the conceptual sense than "human" in the purely biometric sense, that the HARs probably evolved mostly at the formation of the genus Homo. Once there was Homo (Homo erectus?, Homo ergaster?, or is it Homo habilis?), there were humans in the conceptual aspect probably. The development of a modern humankind as ours was just a matter of time, I guess: the pattern of evolution, both biological (bigger better brains) and cultural (improved technologies, symbolism, eventually civilization, I guess) was pretty much already set.

"But the transition erectus>advanced homo (I may include here Heidelb., Neands.,Rudolf.,Sapiens or at least Neands. and Sapiens)seems to me quite fuzzy".

Probably because the transition was fuzzy. I' m sure there was more movement backwards and forwards than is usually conceded. Surviving haplogroups tell us a great deal about migrations over the last 100,000 years or so (but even then are probably not the whole story) although they cannot tell us about earlier movements.

"Minor flows or contacts can perfectly transmit loads of technical practical information without adding almost any genes."

Two notable examples would be the arrival of the Dingo in Australia, probably in a single event that left no discernable genetic trace, and the arrival of the yam from South America to Oceania also probably in a single event leaving no genetic trace on either side of the Pacific.

Not sure about yams (this word means several plants) but think of bananas in Africa, for instance. A lot of technologies have been diffused that way (or some times have been independently developed at several places more or less simultaneously: agriculture, pottery, iron metallurgy - surely others too).

"Because sweet potatoes (Ipomoea batatas) thrive in a hot, moist climate, while potatoes (Solanum tuberosum) require a cool climate, they have never become as popular as the Irish potato in Europe. Sweet potatoes have become an important root crop in warm subtropical and tropical countries, second only to cassava or manioc (Manihot esculenta), a member of the euphorbia family (Euphorbiaceae) and the source of tapioca. Archaeological evidence shows that sweet potatoes were cultivated in South America by 2400 B.C. and fossilized sweet potatoes from the Andes have been dated at 8,000 to 10,000 years old. Although the sweet potato is clearly native to South America, it was also cultivated in Polynesia as early as 1200 A.D. In fact, the sweet potato had already become the principle food of the Maoris in New Zealand by the time of Captain Cook's historic voyage to that part of the world in 1769. It is interesting to note that the sweet potato is known as "kumar" or "kumal" in the Lima region of Coastal Peru, and it is called "kumara" by the Maoris of New Zealand.

In his book, Sea Routes to Polynesia (1968), Thor Heyerdahl postulated that sweet potatoes were carried across the Pacific by Peruvian Indians before Europeans began to sail the world's oceans. He tested his hypothesis in 1947 by sailing a balsa wood raft, the kon-tiki, fashioned after the reed rafts of the Oru Indians living on Lake Titicaca in Bolivia. Although Heyerdahl's hypothesis about the transoceanic exchange of sweet potatoes by skillful pre-columbian sailors remains an enigma (at least to some skeptics)[.]"

The case is refined here with the weight of the evidence strongly favoring Polynesian sea farers bringing sweet potatoes from South American via sea trade and cultural contact. The data of arrival in Polynesia is pushed back about five hundred years and the name similarity reaches Easter Island.

Interesting story that of sweet potatoes (yam is generally the word for another tuber of Old World origin, at least per Wikipedia).

If the Marquesas origin of the sweet potato spread is correct and as these islands are half way between Mexico and Island SE Asia, I am wondering if they were spread first by early Spanish or Portuguese, or even Chinese navigators. However if the 300-700 CE date is correct, then the merit must be of Polynesian sailors without doubt. If Heyerdal could make it, probably Polynesians could too. Yet the ship model he copied is a South American one, so maybe it was a feat by Peruvian native sailors?

Anyhow, back to the dingo, I must remind that the dog appears to have been already domesticated in the context of Aurignacian in Belgium, what is suggestive of even earlier domestication in Asia. These early dogs were probably not too generalized and surely only some bands had them, so maybe dingoes arrived as domestic animals with the earliest settlers of Australia and then the link got lost?

It'd be interesting to know the place of dingos in the genetic context of dogs, which is still somewhat confuse.

"maybe dingoes arrived as domestic animals with the earliest settlers of Australia and then the link got lost?"

That's the generally accepted theory.

"the arrival of the Dingo in Australia, probably in a single event that left no discernable genetic trace"

Any human arrivals would have been swamped genetically by the inhabitants already there. There is still controversy as to when it arrived. But it's agreed somewhere between 6000 and 4000 years ago. And it failed to reach Tasmania. Hence the Tasmanian wolf and Tasmanian devil survived on that island, or did until relatively recently in the case of the wolf.

"If Heyerdal could make it, probably Polynesians could too. Yet the ship model he copied is a South American one, so maybe it was a feat by Peruvian native sailors?"

I don't know if you've read his book but his account of the trip certainly shows that no-one would have wanted to return in the same sort of boat, and do it again. He arrived in the Austral islands, and actually had to be towed ashore. So Polynesians seems to be more likely.

"If the Marquesas origin of the sweet potato spread is correct and as these islands are half way between Mexico and Island SE Asia, I am wondering if they were spread first by early Spanish or Portuguese, or even Chinese navigators. However if the 300-700 CE date is correct, then the merit must be of Polynesian sailors without doubt".

It seems extremely likely that the Spanish introduced the sweet potato to the Philippines and New Guinea. However it's arrival in Eastern Polynesia seems almost certainly pre-Spanish. Marquesas, rather than Easter Island actually makes sense, although I've never heard that theory before. There is some evidence (I forget where I read it now) for pre-European Polynesian presence round the Californian coast somewhere. As far as I know there is no evidence for the sweet potato that far north, but I guess the travellers could have followed the coast south. It would make sense that a people who had been moving rapidly east through islands for several generations would have kept going i n the hope of finding more of them.

"It is interesting to note that the sweet potato is known as 'kumar' or 'kumal' in the Lima region of Coastal Peru, and it is called 'kumara' by the Maoris of New Zealand".

I've read that those Peruvian names are actually mountain names for the vegetable, not coastal. But anyway the kumara's spread through the Pacific remains a mystery.

"... but his account of the trip certainly shows that no-one would have wanted to return in the same sort of boat, and do it again".

Please re-read it. They made an error with the choice of the material for the ropes, so they gradually got loose, what obviously was a problem. However the boat withstood well the journey, even if they had no experience whatsoever traveling in that kind of thing.

Naturally, whatever Polynesian or South American sailors did "the real thing", were much more familiar with that kind of boats and would not commit such errors. In fact, the Polynesians of their island of final arrival immediately knew which was their error and had, Heyerdal says, legends of such boats existing in the past.

"He arrived in the Austral islands, and actually had to be towed ashore".

They crashed against a reef when trying to reach shore in poor conditions. Earlier they found themselves unable to reach some other island because of currents. But they were novices in the art, so this is no evidence of anything.

From Wikipedia:

"Kon-Tiki demonstrated that it was possible for a primitive raft to sail the Pacific with relative ease and safety, especially to the west (with the wind). The raft proved to be highly maneuverable, and fish congregated between the nine balsa logs in such numbers that ancient sailors could have possibly relied on fish for hydration in the absence of other sources of fresh water. Inspired by Kon-Tiki, other rafts have repeated the voyage".

His theories about Polynesian origins are not acceptable today but that says nothing about the journey itself and it is still a very valid conjecture for the spread of the sweet potato, with no appreciable genetic flow implied.

Actually Heryerdal arrived to Tuamotu, not far from the Marquesas, a more than curious coincidence. Maybe some Peruvian traders in their way to/from Mexico (trade between these two regions by sea is confirmed, AFAIK), or between Peru and Ecuador/Colombia, went adrift and ended up in the Marquesas. They probably had a cargo of the tuber with them and that's how all this happened.

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Link: A history of four scientists' fight against harassment in fieldwork
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Kayla Webley Adler of *Marie Claire* magazine has just published an article
recounting the history of the SAFE13 study about sexual harassment and
assaul...